Flexible plate and a flywheel assembly employing the flexible plate

ABSTRACT

A flexible plate is formed with a first rigidity about a first axis and a second rigidity about a second axis where the first and second axis are each perpendicular to a central axia about which the flexible plate is rotatable. The first rigidity is greater than the second rigidity such that the flexible plate may flex more easily about the second axis than the first axis, thus providing the flexible plate with an anisotropic flexural rigidity. In one embodiment, the flexible plate is formed with an eliptical intermediate portion. In another embodiment, the flexible plate includes first and second plates. Each plate has a central portion. The first plate has first foot portions and the second plate has second foot portions. The first and second foot portions have differing circumferential widths.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

A. Field of the Invention

The present invention relates to a flywheel assembly and a flexibleplate of the flywheel assembly.

B. Description of the Prior Art

When the combustion in an engine is converted to torque via acrankshaft, the crankshaft experiences a flexural vibration. Theflexural vibration is transmitted to a flywheel assembly installed inthe end of the crankshaft, leading to a flexural vibration of theflywheel assembly. Furthermore, a corresponding reaction force may causea vibration in the body of a car via an engine block and an enginemount, making a noise during acceleration and during other operatingconditions.

It is necessary to reduce a vibration of a flywheel assembly in order todecrease such a noise during acceleration. For that purpose, a flexibleplate has been placed between a flywheel and the crankshaft. An innercircumference of flexible plate is typically attached to the crankshaft.An outer circumferential portion of the flexible plate is typicallyfixed to the flywheel. The flexible plate is generally rigidity in acircular or circumferential direction but is relatively flexible (lowrigidity) in axial directions such that flexural vibration from thecrankshaft may be absorbed as a result of the axial flexibility. Sincethe flexible plate absorbs a flexural vibration of a crankshaft, thevibration of a flywheel is reduced and noises generated duringacceleration are decreased.

A flexible plate having a low rigidity in axial directions a flexuralvibration more effectively. However, when used with a manualtransmission and a clutch mechanism, if the rigidity of the flexibleplate is too low, the flywheel tends to move in an axial direction whenreleasing the clutch, leading to a ineffective and inefficientdisengagement of the clutch.

SUMMARY OF THE INVENTION

One object of the present invention is provide a flexible plate that isable to absorb a flexural vibration from a crankshaft and thereforereduce noises generated during acceleration but has sufficient rigidityin axial directions to enable reliable disengagement of the clutch.

In accordance with one aspect of the present invention, a flexible platehas an anisotropic flexural rigidity and includes a flywheelinstallation portion on which a flywheel is installable. The flexibleplate also includes a central portion integrally formed with at least aportion of the flywheel installation portion. The central portion isconfigured for installation on a crankshaft an engine. The crankshaftand central portion define a center axis about which the flexible plateand the crankshaft are rotatable. An intermediate portion is formedbetween the flywheel installation portion and the central portion. Afirst and second axis are defined extending through the flywheelinstallation portion and perpendicular to the center axis. Theintermediate portion and the central portion are formed such thatflexural rigidity about the first axis is greater that flexural rigidityabout the second axis.

Preferably, the central portion is axially offset from the flywheelinstallation portion by the intermediate portion.

Preferably, the flywheel installation portion is formed with a pluralityof holes formed at predetermined intervals in a circumferentialdirection to reduce a flexural rigidity about the second axis.

Preferably, the intermediate portion has an elliptical shape.

Preferably, the first and second axis are perpendicular to each other.

Alternatively, the flexible plate also includes a first plate and asecond plate. Each of the first and second plate are formed withseparate annular central portions fixed to one another to define thecentral portion. The first plate is formed with first foot portionsextending in opposite radial directions outward from the annular centralportion of the first plate. The second plate is formed with second footportions extending in opposite radial directions outward from theannular central portion of the second plate. The first foot portions andthe second foot portions define the intermediate portion and theflywheel installation portion. The first foot portions and the secondfoot portions are perpendicular to one another with respect to thecentral axis. The first foot portions is generally aligned with thefirst axis and the second foot portions is generally aligned with thesecond axis. A circumferential width of the second foot portions isgreater that a circumferential width of the first foot portions.

Preferably, the first foot portions are symmetrical about the firstaxis, and the second foot portions are symmetrical about the secondaxis.

Preferably, an axial thickness of the first plate differs from an axialthickness of the second plate.

In accordance with another aspect of the present invention, a flexibleplate has an anisotropic flexural rigidity and includes a flywheelinstallation portion on which a flywheel is installable and a centralportion integrally formed with at least a portion of the flywheelinstallation portion. The central portion is configured for installationon a crankshaft an engine. The crankshaft and central portion define acenter axis about which the flexible plate and the crankshaft arerotatable. An elliptically shaped intermediate portion is formed betweenthe flywheel installation portion and the central portion. Generallyperpendicular first and second axis are defined extending through andperpendicular to the center axis, and the flywheel installation portion,the intermediate portion and the central portion are formed such thatflexural rigidity about the first axis is greater that flexural rigidityabout the second axis.

Preferably, the central portion is axially offset from the flywheelinstallation portion by the intermediate portion.

Preferably, the flywheel installation portion is formed with a pluralityof holes formed at predetermined intervals in a circumferentialdirection to reduce a flexural rigidity about the second axis.

In accordance with another aspect of the present invention, a flexibleplate has an anisotropic flexural rigidity and includes a first plateand a second plate. Each of the first and second plates is formed withseparate annular central portions fixed to one another. The annularcentral portion is configured for installation on a crankshaft anengine. The crankshaft and the annular central portions define a centeraxis about which the first and second plates and the crankshaft arerotatable. The first plate is formed with a first foot portion radiallyoutward from the annular central portion of the first plate. The secondplate is formed with a second foot portion extending radially outwardfrom the annular central portion of the second plate. The first footportion and the second foot portion are circumferentially offset fromone another with respect to the central axis. The first and secondportions define a flywheel installation portion on which a flywheel isinstallable. A first axis is defined by the first foot portion and asecond axis is defined by the second foot portion such that flexuralrigidity about the first axis is greater that flexural rigidity aboutthe second axis.

Preferably, a circumferential width of the second foot portion isgreater that a circumferential width of the first foot portion.

Preferably, the first plate is formed with two of the first footportions, the first foot portions extending radially outward in oppositedirections, and the second plate is formed with two of the second footportions extending radially outward in opposite directions. The firstfoot portions are symmetrical with respect to the center axis, and thesecond foot portions are symmetrical with respect to the center axis.

Preferably, an axial thickness of the first plate differs from an axialthickness of the second plate.

In the flexible plate in accordance with the present invention, flexuralvibrations from a crankshaft of an engine are adsorbed within a certainrange of frequency and amplitude, due to the flexing ability of theflexible plate about one axis, but limited flexing ability in aboutanother axis, where both axis are perpendicular to a central axis of theflexible plate. Thus, the flexible plate plays a role in preventingtransmission of a certain range of flexural vibration from a crankshaftto a flywheel.

The flexural vibration absorbing characteristics of the flexible platecan be manipulated and fine tuned by any of a number of additionalfeatures. For example, adding holes to the flexible plate in strategicpositions can add more flexibility to those sections of the flexibleplate. In the embodiment where two plates are used, the circumferentialwidth of the foot portions can be manipulated to change thecharacteristics of the flexible plate. Further, in the embodiment wheretwo plates are used, the thickness of each plate can be manipulated toalter the flexural vibration absorbing characteristics. In theembodiment where an intermediate portion has an elliptical shape, thesize and depth of the intermediate portion can be manipulated to enhancethe flexural vibration absorbing characteristics of the flexible plate.Also, in the embodiment where an intermediate portion has an ellipticalshape, the central portion and the flywheel installation portion may beoffset axially from one another. The offset dimension may also bemanipulated to enhance the flexural vibration absorbing characteristicsof the flexible plate.

These and other objects, features, aspects and advantages of the presentinvention will become more fully apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings where like reference numerals denote correspondingparts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, side cross section of a flywheel assemblyhaving a flexible plate in accordance with a first embodiment of thepresent invention;

FIG. 2 is an end elevational view of the flexible plate in accordancewith the first embodiment of the invention, shown removed from theflywheel assembly depicted in FIG. 1; and

FIG. 3 is an end elevational view similar to FIG. 2, showing a flexibleplate in accordance with a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

FIG. 1 shows a flywheel assembly 1 in accordance with a first embodimentof the present invention and a clutch device 2 which is attached to theflywheel assembly 1. In FIG. 1, the line 0--0 represents a central axisabout which the clutch device and the flywheel assembly are rotatable.

The flywheel assembly 1 is installed on an end portion of a crankshaft3, and includes a flexible plate 4 and a flywheel 5.

The flexible plate 4 has a disk like shape and is formed with a centerhole 4a. The flexible plate 4 is generally formed with two portions, aninner circumferential portion 4b and an outer circumferential portion4c. The inner circumferential portion 4b of the flexible plate 4 isfixed to a flange part 3a of the crankshaft 3 by bolts 6. The bolts 6passes through holes 10 which are formed in the inner circumferentialportion 4b. The flywheel 5 is fixed to the outer circumferential portion4c by bolts 7. The bolts 7 pass through holes 11 which are formed in theouter circumferential portion 4c. A plurality of pierced holes 8 areformed in the intermediate portion 4d between the inner and outercircumferential parts 4b and 4c. The plurality of pierced holes 8 arelocated at predetermined intervals in a circular direction as shown inFIG. 2.

An elliptical drawn portion 12 is formed between the innercircumferential portion 4b and the outer circumferential portion 4c ofthe flexible plate 4. The elliptical drawn portion 12 provides atransition between the inner circumferential portion 4b and the outercircumferential portion 4c in the axial direction, as shown in FIG. 1.Specifically, the inner circumferential portion 4b is axially offsetfrom the outer circumferential portion 4c.

The flexible plate 4 has a flexural and translational rigidities both ofwhich are reduced by the presence of pierced holes 8. Since piercedholes 8 are located at offset intervals, as shown in FIG. 2, theflexible plate 4 has an anisotropic flexural rigidity. The presence ofthe elliptical drawn portion 12 increases a flexural rigidity withrespect to deflection about the x-axis without substantially increasinga flexural rigidity with respect to deflection about the y-axis.Therefore, the formations of pierced holes 8 and the elliptical drawnportion 12 reduces a flexural rigidity around y-axis without decreasingtranslational (rotation) rigidity.

The flywheel 5 has a generally disk like shape and has a frictionsurface 5a formed thereon, as shown in FIG. 1.

The clutch device 2 includes a clutch cover assembly 20 and a clutchdisk assembly 21 which is disposed between the clutch cover assembly 20and the flywheel 5. The clutch cover assembly 20 includes a clutch cover22 which is fixed to the outer circumferential part of the flywheel 5, apressure plate 23 which urges the clutch disk assembly 21 against thefriction surface 5a of the flywheel 5, and a diaphragm spring 24 whichbiases the pressure plate 23 against the flywheel 5.

The operation of the present invention is as follows.

When the combustion of the engine (not shown) is converted to torque viathe crankshaft 3, the crankshaft 3 typically experiences a flexuralvibration to due the combustion process. Torque and flexural vibrationare transmitted to the flexible plate 4 which is fixed to the crankshaft3. The torque is transmitted to the flywheel 5 which is installed in theouter circumferential portion 4c of the flexible plate 4, thentransmitted to the clutch disk assembly 21 which is engaged between theflywheel 5 and the pressure plate 23, and further transmitted to thetransmission (not shown) which is connected to the clutch disk assembly21. On the other hand, the flexural vibrations from the crankshaft 3 areat least partially absorbed by the flywheel 5 because of low rigidity ofthe flexible plate 4. As the result, the vibration experienced in thebody of the car equipped with the present invention is reduced becauseat least a portion, if not all, of flexural vibration is absorbed by theflexible plate 4 of the flywheel assembly 1, and noises duringacceleration are reduced.

In the present embodiment, the flexible plate 4 is designed to absorbflexural vibration that occurs primarily about the y-axis. Therefore, itis preferable to install the flexible plate 4 on the crankshaft 3 sothat flexural vibration coincides or is about the y-axis in FIG. 2. Theflexural rigidity of the flexible plate 4 which absorbs a flexuralvibration between the crankshaft 3 and the flywheel 5 is the flexuralrigidity about the y-axis which is lower than that in other directions.On the other hand, the flexural rigidity about x-axis is relatively highso that there is little flexing of the flexible plate 4 about thex-axis, and hence little vibration absorption about the x-axis. Therigidity about the x-axis also provides an axial rigidity to theflexible plate 4 that limits axial displacement during clutch engagementand disengagement. In other words, the elliptical drawing portion 12provides the flexible plate 4 with an axial rigidity that limits axialdeflection of the flexible plate 4 where axial forces are appliedgenerally along the central axis 0--0 or the flywheel assembly 1.However, when vibrations are applied to the flywheel assembly where thevibrations occur about the y-axis shown in FIG. 2, the flexible plate 4easily deflects, thus absorbing vibration. About the x-axis, theflexible plate 4 is relatively rigid.

Thus, since the flexible plate 4 has an anisotropic flexural rigidity,the flexural rigidity around y-axis can be reduced, while keeping thewhole translational rigidity of the flexible plate 4. Therefore, theflexible plate 4 can absorb more flexural vibration without reducingaxial rigidity necessary for disengagement and engagement of the clutchmechanism. In addition, since the translational rigidity and theflexural rigidity around y-axis can be set up independently by adjustingthe location and size of pierced holes 8 and the shape and size of theelliptical drawing portion 12, it is possible to separate resonancefrequencies (characteristic frequency) of two modes, a translation and aflexure, of a flywheel assembly 1 by optimizing the translational andflexural rigidities. Thus, the damping ability of a flexural vibrationof a flywheel assembly 1 is improved.

Second Embodiment

While the flexible plate 4 as shown in FIG. 2 is used in the firstembodiment, a flexible plate 14 in accordance with a second embodimentmay also be employed, as shown in FIG. 3.

The flexible plate 14 is formed from plates 30 and 40 which are fixed byrivets not shown in FIG. 3. Plates 30 and 40 include disk-like centralportions 31 and 41, respectively, each having center holes 31a and 41a,respectively. The plates 30 and 40 are further formed with a pair ofoppositely extending foot portions 32 and 42, respectively, which extendoutward in opposite radial direction from the central portions 31 and41, respectively. A plurality of holes 31b and 41b are formed in thecentral portions 31 and 41, respectively. The central portions 31 and 41may be fixed to the flange portion 3a of the crankshaft 3 by bolts 6which pass through holes 31b and 41b. Rivets holes 31c and 41c areformed in the outer circumferential parts of the central portions 31 and41. The plates 30 and 40 are connected to each other by rivets (notshown) which extend through holes 31c and 41c. When the plates 30 and 40are connected, the angle defined between both foot portions 32 and 42 is90°. Holes 32d and 42d are formed at outer radial portions of the footportions 32 and 42, respectively. The flywheel 5 may be attached to thefoot portions 32 and 42 by bolts 7 which pass through the holes 32d and42d.

The foot portions 32 and 42 define a flywheel installation portion inthe area around the holes 32d and 42d, respectively. The area betweenthe holes 32d and 42d and the central portions 31 and 41 of the footportions 32 and 42 define intermediate portions of the flexible plate14.

The flexible plate 14 has a small flexural rigidity around y-axis,because the width of the foot portion 42 of the plate 40 is small. Onthe other hand, it has a large flexural rigidity around x-axis, sincethe width of the foot portion 32 of the plate 30 is large. Thus, whilethe whole translational rigidity (rotational rigidity) of the flexibleplate 14 is generally large, the flexural rigidity around y-axis is setup to be so small that the flexible plate 14 adsorbs at least a portionof flexural vibration.

The flexible plate 14 in the present embodiment has an anisotropicflexural rigidity and can absorb a flexural vibrations without losingthe axial rigidity necessary for continuous engagement and disengagementof the clutch mechanism. By separating positively resonance frequencies(characteristic frequency) of two modes, translation and flexure, of aflywheel assembly 1, the damping ability of a flexural vibration of aflywheel assembly 1 is improved.

In the flexible plate 14, the plate 30 (in combination with the plate40) provides an axial rigidity able to withstand engagement anddisengagement of the clutch mechanism. The plate 40 having smaller footportions 42 than the foot portions 32 of the plate 30, enables theflexible plate 14 to undergo greater flexing about the y-axis than thex-axis. Further the two plates 30 and 40 provide circumferentialrigidity insuring efficient transmission of torque.

In the present embodiment, the central portions 31 and 41 of theflexible plate 14 are fixed to the crankshaft 3. The central portions 31and 41 are, from a structural point of view, very important becauselarge torque forces are experienced due to the connection between thetwo plates 30 and 40 and the crankshaft. Therefore, central portions 31and 41 being fixed to each other provide a large flexural rigidity,leading to a reduction in localized stress. Thus, the flexible plate 14has a optimized structure in which the part receiving a large amount oftorque has a large rigidity without increasing the flexural rigidity ofthe entire flexible plate.

In the present embodiment, the flexible plate 14 is formed using twoplates, each plate having foot portions 32 and 42 extending in oppositedirections from the central portions 31 and 41, respectively. It is alsopossible to form a flexible plate which has more than two plates withfoot portions extending from a central portion thereof.

Alternate Embodiment

In the above second embodiment, the flexural rigidities of both plates30 and 40 differ owing to the different width of foot portions 32 and42. It is also possible to make difference in the flexural rigidityowing to the different thickness of a plate or the presence of holes,instead of the different width of foot portions.

In the above first and second embodiments, a flywheel assembly 1 doesnot have a dampening mechanism to damp a torsional vibration which iscaused by a crankshaft 3. It is also possible to apply a flexible plateof the present invention to a separated type of flywheel which has adampening mechanism between divided flywheels.

The Effect of the Invention

Since the flexible plate of the present invention has an anisotropicflexural rigidity, it is possible to reduce a flexural rigidity in acertain direction without changing a translational rigidity. Therefore,without losing the sharpness of the disengagement of the clutch, theflexible plate can absorb more flexural vibration of a crankshaft andreduce noise during acceleration than prior art flexible plates.

Various details of the invention may be changed without departing fromits spirit nor its scope. Furthermore, the foregoing description of theembodiments according to the present invention is provided for thepurpose of illustration only, and not for the purpose of limiting theinvention as defined by the appended claims and their equivalents.

What is claimed is:
 1. A flexible plate which has an anisotropicflexural rigidity, comprising:a flywheel installation portion on which aflywheel is installable; a central portion integrally formed with atleast a portion of said flywheel installation portion, said centralportion being configured for installation on a crankshaft an engine, thecrankshaft and central portion defining a center axis about which theflexible plate and the crankshaft are rotatable; and an ellipticallyshaped intermediate portion formed between said flywheel installationportion and said central portion; wherein first and second axis aredefined extending through said elliptically shaped intermediate portion,said first and second axis are perpendicular to one another andintersect the center axis, said first and second axis beingperpendicular to the center axis, and, said flywheel installationportion, said intermediate portion and said central portion are formedsuch that flexural rigidity about said first axis is greater thatflexural rigidity about said second axis.
 2. The flexible plate as setforth in claim 1, wherein said central portion is axially offset fromsaid flywheel installation portion.
 3. The flexible plate as set forthin claim 1, wherein said flywheel installation portion is formed with aplurality of holes formed at predetermined intervals in acircumferential direction to reduce a flexural rigidity about saidsecond axis.